Piezoelectric film sensor and method for manufacturing piezoelectric film sensor

Abstract

To provide a piezoelectric film sensor capable of suppressing spring back even when stuck to a curved surface part of an adherend.SOLUTION: A piezoelectric film sensor has a laminate structure in which a piezoelectric film having a first main surface and a second main surface, a first electrode disposed on the first main surface, a second electrode disposed on the second main surface, and a first substrate disposed between the second electrode and an adherend are laminated, in which the laminate structure is curved in a convex shape in a first direction from the first substrate toward the first electrode in a cross-sectional view.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric film sensor and a method for manufacturing a piezoelectric film sensor. [Background technology]

[0002] Patent Document 1 discloses a structure in which a piezoelectric film sensor is attached to the side surface of a cylindrical housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2012 / 137897 Summary of the Invention [Problem to be solved by the invention]

[0004] If a flat piezoelectric film sensor is attached to a curved surface of an adherend such as the side surface of a cylinder, the piezoelectric film sensor may peel off due to spring back.

[0005] An object of the present invention is to provide a piezoelectric film sensor that can suppress springback even when attached to a curved surface of an adherend. [Means for solving the problem]

[0006] The piezoelectric film sensor of this invention is a piezoelectric film sensor having a laminate structure in which a piezoelectric film having a first main surface and a second main surface, a first electrode arranged on the first main surface, a second electrode arranged on the second main surface, and a first substrate arranged between the second electrode and an adherend, and is characterized in that, when viewed in cross section, the laminate structure is convexly curved in a first direction from the first substrate toward the first electrode.

[0007] In this way, when viewed in cross section, the piezoelectric film sensor is convexly curved in the first direction from the first substrate to the first electrode, thereby suppressing springback even when attached to a curved portion of an adherend. [Effects of the Invention]

[0008] According to this invention, springback can be suppressed even when the adhesive is attached to a curved surface of an adherend. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of an adherend 1 to which a piezoelectric film sensor 10 is attached. [Figure 2] 2 is an enlarged partial cross-sectional view of the piezoelectric film sensor 10 and the housing 30. FIG. [Figure 3] 2 is a cross-sectional view of the piezoelectric film sensor 10 before being attached to the housing 30. FIG. [Figure 4] 2 is a cross-sectional view of the piezoelectric film sensor 10 before being attached to the housing 30. FIG. [Figure 5] 10 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10A and a housing 30 according to a first modification. FIG. [Figure 6] 10 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10C and a housing 30 according to a third modification. FIG. [Figure 7] 10 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10D and a housing 30 according to a fourth modification. FIG. [Figure 8] 10 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10E and a housing 30 according to a fifth modification. FIG. [Figure 9] 13 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10F and a housing 30 according to a sixth modification. FIG. [Figure 10] 13 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10G and a housing 30 according to a seventh modification. FIG. [Figure 11] 13 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10H and a housing 30 according to Modification 8. FIG. [Figure 12]10 is a cross-sectional view of the piezoelectric film sensor 10 before it is attached to the housing 30, and shows a first modified example of the method for manufacturing the piezoelectric film sensor 10. FIG. [Figure 13] 10 is a cross-sectional view of the piezoelectric film sensor 10 before it is attached to the housing 30, and shows a second modified example of the method for manufacturing the piezoelectric film sensor 10. FIG. [Figure 14] FIG. 10 is a schematic diagram showing a third modified example of the manufacturing method. DETAILED DESCRIPTION OF THE INVENTION

[0010] FIG. 1 is a perspective view of an adherend 1 to which a piezoelectric film sensor 10 of this embodiment is attached. The adherend 1 has a cylindrical housing 30. The piezoelectric film sensor 10 is attached to the cylindrical side surface of the housing 30. A user holds the housing 30 near both ends with both hands and twists the housing 30. By twisting the housing 30, the user can, for example, perform muscle training. The piezoelectric film sensor 10 detects torsional deformation occurring in the housing 30, for example. The shape of the housing 30 is not limited to a cylinder. For example, it may have an elliptical or polygonal cross-sectional shape.

[0011] 2 is an enlarged partial cross-sectional view of the piezoelectric film sensor 10 and the housing 30. The piezoelectric film sensor 10 has a first electrode 50, a piezoelectric film 20, a second electrode 55, a first substrate 70, and an adhesive 90.

[0012] The first electrode 50 is disposed on a first main surface of the piezoelectric film 20. The first electrode 50 is, for example, an adhesive and conductive tape member. The first electrode 50 is grounded and functions as a ground electrode.

[0013] The piezoelectric film 20 is a piezoelectric material that generates polarization on opposing first and second principal surfaces (upper and lower surfaces) due to expansion and contraction. For example, the piezoelectric film is made of uniaxially stretched polylactic acid (PLA) or PVDF. The polylactic acid is either L-type polylactic acid (PLLA) or D-type polylactic acid (PDLA). Since polylactic acid generates piezoelectricity through molecular orientation treatment such as stretching, there is no need for poling treatment like with other polymers such as PVDF or piezoelectric ceramics. Furthermore, polylactic acid does not exhibit pyroelectric properties. Therefore, polylactic acid does not generate polarization due to the user's body temperature, making it suitable for use in devices that are touched by the user, such as the present embodiment.

[0014] The second electrode 55 is disposed on the second main surface of the piezoelectric film 20. The second electrode 55 is formed on the upper surface of the first substrate 70 by printing or the like. The second electrode 55 functions as a signal electrode for detecting a voltage generated on the second main surface of the piezoelectric film 20.

[0015] Alternatively, the first electrode 50 may be a signal electrode and the second electrode 55 may be a ground electrode.

[0016] The first substrate 70 is disposed between the second electrode 55 and the housing 30, which is the adherend. The first substrate 70 is a flexible insulating substrate made of, for example, polyimide, PET, or liquid crystal polymer. The first substrate 70 is attached to the housing 30 of the adherend 1 via an adhesive 90.

[0017] A detection circuit (not shown) measures the potential difference (voltage) between the first electrode 50 and the second electrode 55. When the detection circuit detects a voltage that exceeds a predetermined threshold, for example, it determines that the housing 30 has been twisted by the user.

[0018] As shown in FIG. 2 , the piezoelectric film sensor 10 is curved convexly in a first direction from the housing 30 toward the first electrode 50 in a cross-sectional view. FIGS. 3 and 4 are cross-sectional views of the piezoelectric film sensor 10 before it is attached to the housing 30 and illustrate a manufacturing method for the piezoelectric film sensor 10. The piezoelectric film sensor 10 has a laminate structure in which a piezoelectric film 20, a first electrode 50, a second electrode 55, and a first substrate 70 are stacked. As shown in FIG. 3 , the piezoelectric film sensor 10 is planar when the laminate structure is formed. If the planar piezoelectric film sensor 10 were directly attached to the curved housing 30, springback could cause the piezoelectric film sensor 10 to peel off from its edge. Therefore, as shown in FIG. 4 , the piezoelectric film sensor 10 of this embodiment is placed on a jig 301 having a curved surface with a predetermined curvature and pulled in the planar direction. Because each layer of the piezoelectric film sensor 10 is placed on the jig 301 having a curved surface, it is pulled in the direction opposite to the first direction. By being pulled in the direction opposite to the first direction, the layer closest to the jig 301 (first substrate 70) stretches the shortest, and the layer farthest from the jig 301 (first electrode 50) stretches the longest. As a result, the piezoelectric film sensor 10 curves convexly in the first direction.

[0019] In this way, the piezoelectric film sensor 10 of this embodiment is pre-curved convexly in the first direction, so that springback can be suppressed even when it is attached to the housing 30 of the adherend 1, which has a curved surface shape.

[0020] Furthermore, the piezoelectric film 20 of this embodiment is disposed above the center in the first direction of the laminate structure. When the housing 30 is bent upward, for example, the bottom side of the piezoelectric film sensor 10 contracts and the top side expands. That is, a non-expanding portion (a stress neutral plane) exists inside the piezoelectric film sensor 10. If the piezoelectric film 20 were disposed in the center in the first direction of the laminate structure, the stress neutral plane might overlap with the position of the piezoelectric film 20. If the stress neutral plane overlaps with the position of the piezoelectric film 20, a large output might not be obtained from the piezoelectric film 20. However, because the piezoelectric film 20 of this embodiment is disposed above the center in the first direction of the laminate structure, the position of the piezoelectric film 20 is away from the stress neutral plane. Therefore, the piezoelectric film 20 can generate a large electric charge in response to the deformation of the housing 30.

[0021] (Variation 1) Fig. 5 is an enlarged partial cross-sectional view of the piezoelectric film sensor 10A and the housing 30 according to Modification 1. The same reference numerals are used to designate components common to Fig. 2, and a description thereof will be omitted. Note that, for ease of explanation, Fig. 5 shows the piezoelectric film sensor 10A and the housing 30 as planar shapes, but in reality, the piezoelectric film sensor 10A and the housing 30 have curved shapes, and the piezoelectric film sensor 10A is curved convexly in the first direction.

[0022] The piezoelectric film sensor 10 includes a first electrode 50, a piezoelectric film 20, a second electrode 55, a first substrate 70, a third electrode 57, a second substrate 75, and an adhesive 90. The third electrode 57 is disposed below the first substrate 70 in the direction opposite to the first direction. The second substrate 75 is disposed below the third electrode 57.

[0023] In the first modification, the first electrode 50 and the third electrode 57 are ground electrodes, and the second electrode 55 is a signal electrode. This electrically shields the top and bottom surfaces of the piezoelectric film sensor, improving noise resistance and providing stable sensitivity.

[0024] Furthermore, in the piezoelectric film sensor 10A of the first modification, the third electrode 57 and the second substrate 75 are disposed below the piezoelectric film 20, so that the piezoelectric film 20 is positioned further away from the neutral plane of stress. Therefore, the piezoelectric film 20 can generate a higher charge in response to the deformation of the housing 30.

[0025] (Variation 2) The piezoelectric film sensor 10B according to the second modification has the same structure as the piezoelectric film sensor 10A shown in Fig. 5. However, the second substrate 75 according to the second modification has a lower rigidity than the first substrate 70, making it more susceptible to deformation. For example, the second substrate 75 is made of a material with a lower elastic modulus than the first substrate 70.

[0026] In the piezoelectric film sensor 10B of the second modification, the second substrate 75 has a lower rigidity than the first substrate 70, making it easier to deform, and therefore easier to bend convexly in the first direction.

[0027] (Variation 3) Fig. 6 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10C and a housing 30 according to Modification Example 3. The same components as those in Fig. 5 are denoted by the same reference numerals, and a description thereof will be omitted. Note that, for ease of explanation, the piezoelectric film sensor 10C and the housing 30 are shown in planar shapes in Fig. 6 as well, but in reality, the piezoelectric film sensor 10C and the housing 30 have curved shapes, and the piezoelectric film sensor 10C is curved convexly in the first direction.

[0028] Second base material 75A according to Modification 3 is divided into multiple members. As a result, second base material 75A according to Modification 3 also has lower rigidity than first base material 70, making it more susceptible to deformation. Second base material 75A may be made of a material with the same elastic modulus as first base material 70, or may be made of a material with a lower elastic modulus than first base material 70.

[0029] In the piezoelectric film sensor 10C of the third modification, the second substrate 75A has lower rigidity than the first substrate 70, making it easier to deform, and therefore easier to bend convexly in the first direction.

[0030] (Variation 4) Fig. 7 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10D and a housing 30 according to Modification 4. The same components as those in Fig. 6 are denoted by the same reference numerals, and a description thereof will be omitted. Note that, for ease of explanation, the piezoelectric film sensor 10D and the housing 30 are shown in planar shapes in Fig. 7 as well, but in reality, the piezoelectric film sensor 10D and the housing 30 have curved shapes, and the piezoelectric film sensor 10D is curved convexly in the first direction.

[0031] The second base material 75B according to the fourth modification is divided into a plurality of members. The second base material 75B divided into a plurality of members is arranged separately from each other. As a result, the rigidity of the second base material 75B according to the fourth modification is also lower than the rigidity of the first base material 70, making it more susceptible to deformation. The second base material 75B may be made of a material having the same elastic modulus as the first base material 70, or may be made of a material having a lower elastic modulus than the first base material 70.

[0032] In the piezoelectric film sensor 10D of the fourth modification, the second substrate 75B has lower rigidity than the first substrate 70, making it easier to deform, and therefore easier to bend convexly in the first direction.

[0033] (Variation 5) Fig. 8 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10E and a housing 30 according to Modification 5. The same components as those in Fig. 5 are denoted by the same reference numerals, and a description thereof will be omitted. Note that, for ease of explanation, the piezoelectric film sensor 10E and the housing 30 are shown in planar shapes in Fig. 8 as well, but in reality, the piezoelectric film sensor 10E and the housing 30 have curved shapes, and the piezoelectric film sensor 10E is curved convexly in the first direction.

[0034] The second substrate 75C according to Modification 5 has a notch 750. The notch 750 is formed on the upper surface of the second substrate 75C. As a result, the rigidity of the second substrate 75C according to Modification 5 is also lower than the rigidity of the first substrate 70, making it more susceptible to deformation. The second substrate 75C may be made of a material with the same modulus of elasticity as the first substrate 70, or may be made of a material with a modulus of elasticity lower than that of the first substrate 70.

[0035] In the piezoelectric film sensor 10E of the fifth modification, the second substrate 75C has lower rigidity than the first substrate 70, making it easier to deform, and therefore easier to bend convexly in the first direction.

[0036] (Variation 6) Fig. 9 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10F and a housing 30 according to Modification Example 6. The same components as those in Fig. 5 are denoted by the same reference numerals, and a description thereof will be omitted. Note that, for ease of explanation, the piezoelectric film sensor 10F and the housing 30 are shown in planar shapes in Fig. 9 as well, but in reality, the piezoelectric film sensor 10F and the housing 30 have curved shapes, and the piezoelectric film sensor 10F is curved convexly in the first direction.

[0037] A second base material 75D according to Modification 6 has a notch 750. The notch 750 is formed on the lower surface of the second base material 75D. As a result, the rigidity of the second base material 75D according to Modification 6 is also lower than the rigidity of the first base material 70, making it more susceptible to deformation. The second base material 75D may be made of a material with the same modulus of elasticity as the first base material 70, or may be made of a material with a modulus of elasticity lower than that of the first base material 70.

[0038] In the piezoelectric film sensor 10F of the sixth modification, the second substrate 75D has lower rigidity than the first substrate 70, making it easier to deform, and therefore easier to bend convexly in the first direction.

[0039] (Variation 7) Fig. 10 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10G and a housing 30 according to Modification Example 7. The same components as those in Fig. 5 are denoted by the same reference numerals, and a description thereof will be omitted. Note that, for ease of explanation, the piezoelectric film sensor 10G and the housing 30 are shown in planar shapes in Fig. 10 as well, but in reality, the piezoelectric film sensor 10G and the housing 30 have curved shapes, and the piezoelectric film sensor 10G is curved convexly in the first direction.

[0040] The second base material 75E according to Modification Example 7 is divided into multiple members. The second base material 75E divided into multiple members each has a tapered chamfered lower surface. However, the second base material 75E may not be divided into multiple members, but may simply have tapered grooves. This makes the rigidity of the second base material 75E according to Modification Example 7 lower than the rigidity of the first base material 70, making it more easily deformable. The second base material 75E may be made of a material with the same elastic modulus as the first base material 70, or may be made of a material with a lower elastic modulus than the first base material 70.

[0041] In the piezoelectric film sensor 10G of the seventh modification, the second base material 75E has lower rigidity than the first base material 70, making it easier to deform, and therefore easier to bend convexly in the first direction.

[0042] (Variation 8) Fig. 11 is an enlarged partial cross-sectional view of a piezoelectric film sensor 10H and a housing 30 according to Modification 8. The same components as those in Fig. 5 are denoted by the same reference numerals, and a description thereof will be omitted. Note that, for ease of explanation, the piezoelectric film sensor 10H and the housing 30 are shown in planar shapes in Fig. 11 as well, but in reality, the piezoelectric film sensor 10H and the housing 30 have curved shapes, and the piezoelectric film sensor 10H is curved convexly in the first direction.

[0043] The second substrate 75F according to Modification 8 is thinner than the first substrate 70. As a result, the rigidity of the second substrate 75F according to Modification 8 is also lower than the rigidity of the first substrate 70, making it more susceptible to deformation. The second substrate 75F may be made of a material with the same modulus of elasticity as the first substrate 70, or may be made of a material with a modulus of elasticity lower than that of the first substrate 70.

[0044] In the piezoelectric film sensor 10H of the eighth modification, the second substrate 75F has lower rigidity than the first substrate 70, making it easier to deform, and therefore easier to bend convexly in the first direction.

[0045] (Manufacturing method variation 1) FIG. 12 is a cross-sectional view of the piezoelectric film sensor 10 before it is attached to the housing 30, and illustrates a first modified example of the manufacturing method for the piezoelectric film sensor 10. In the manufacturing method shown in FIG. 4, the piezoelectric film sensor 10 is placed on a jig 301 and pulled in a planar direction. In the example shown in FIG. 12, the piezoelectric film sensor 10 is placed on the jig 301 and pressure-bonded. In this case, the piezoelectric film sensor 10 is also curved convexly in the first direction.

[0046] (Manufacturing method variation 2) Fig. 13 is a cross-sectional view of the piezoelectric film sensor 10 before being attached to the housing 30, and illustrates a second modified example of the manufacturing method for the piezoelectric film sensor 10. In the manufacturing method shown in Fig. 12, the piezoelectric film sensor 10 is placed on a jig 301 and pressure-bonded, but in the example of Fig. 13, the jig 301 is placed on the first substrate 70 of the piezoelectric film sensor 10 and pressure-bonded. In this case as well, the piezoelectric film sensor 10 is curved convexly in the first direction.

[0047] (Manufacturing method variation 3) Fig. 14 is a schematic diagram showing a third modified example of the manufacturing method. In the example of Fig. 14, the piezoelectric film sensor 10 is sandwiched between three rollers (a first roller 101, a second roller 102, and a third roller 103) and stretched. The first substrate 70 of the piezoelectric film sensor 10 contacts the second roller 102, and the first electrode 50 contacts the first roller 101 and the third roller 103. The second roller 102 is disposed so as to face the first roller 101 and the third roller 103 with the piezoelectric film sensor 10 sandwiched therebetween. The first roller 101 and the third roller 103 are disposed side by side on the first electrode 50 side of the piezoelectric film sensor 10.

[0048] As a result, when the piezoelectric film sensor 10 is stretched, the first electrode 50 stretches the longest, and the piezoelectric film sensor 10 is curved in a convex shape in the first direction.

[0049] The description of the present embodiment is illustrative in all respects and is not restrictive. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications that are equivalent to the claims and fall within the scope thereof.

[0050] The technical concept of this embodiment can be summarized as follows.

[0051] (1) a piezoelectric film having a first major surface and a second major surface; a first electrode disposed on the first main surface; a second electrode disposed on the second main surface; a first substrate disposed between the second electrode and an adherend; A piezoelectric film sensor having a laminated structure in which The piezoelectric film sensor is characterized in that, in a cross-sectional view, it is curved convexly in a first direction from the first substrate toward the first electrode. Piezoelectric film sensor.

[0052] (2) the piezoelectric film is disposed above the center of the laminate structure in the first direction; The piezoelectric film sensor according to (1) above.

[0053] (3) The piezoelectric film has the highest linear expansion coefficient of any of the members constituting the laminate structure. The piezoelectric film sensor according to (1) or (2) above.

[0054] (4) a third electrode disposed under the first substrate in a direction opposite to the first direction; a second substrate disposed below the third electrode; The piezoelectric film sensor according to any one of (1) to (3) above, further comprising:

[0055] (5) The rigidity of the second substrate is lower than the rigidity of the first substrate. The piezoelectric film sensor according to (4) above.

[0056] (6) The second base material is divided into a plurality of members. The piezoelectric film sensor according to (5) above.

[0057] (7) The second base material divided into a plurality of members is arranged at a distance from each other. The piezoelectric film sensor according to (6) above.

[0058] (8) The second substrate is thinner than the first substrate. The piezoelectric film sensor according to any one of (5) to (7) above.

[0059] (9) The second substrate has a notch. The piezoelectric film sensor according to any one of (5) to (7) above.

[0060] (10) The notch is disposed below the second base material in a direction opposite to the first direction. The piezoelectric film sensor according to (9) above.

[0061] (11) a piezoelectric film having a first major surface and a second major surface; a first electrode disposed on the first main surface; a second electrode disposed on the second main surface; a first substrate disposed between the second electrode and an adherend; are laminated to form a laminate structure, The laminate structure is placed on a curved surface and pulled from both ends to bend it convexly in a first direction from the first substrate toward the first electrode. Manufacturing method of piezoelectric film sensor. [Explanation of symbols]

[0062] 1: Adherent 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H: Piezoelectric film sensor 20: Piezoelectric film 30: Housing 50: 1st electrode 55: 2nd electrode 57:Third electrode 70: 1st base material 75,75A,75B,75C,75D,75E,75F: 2nd base material 90: Adhesive 101: First roller 102: Second roller 103: Third Roller 301: Jig 750: Notch

Claims

1. a piezoelectric film having a first major surface and a second major surface; a first electrode disposed on the first major surface; a second electrode disposed on the second main surface; a first substrate disposed between the second electrode and an adherend; A piezoelectric film sensor having a laminated structure in which The piezoelectric film sensor is characterized in that, in a cross-sectional view, it is curved convexly in a first direction from the first substrate toward the first electrode. Piezoelectric film sensor.

2. the piezoelectric film is disposed above the center of the laminate structure in the first direction; The piezoelectric film sensor according to claim 1 .

3. The piezoelectric film has the highest linear expansion coefficient of any of the members constituting the laminate structure. The piezoelectric film sensor according to claim 1 .

4. a third electrode disposed under the first substrate in a direction opposite to the first direction; a second substrate disposed below the third electrode; The piezoelectric film sensor of claim 1 further comprising:

5. The rigidity of the second substrate is lower than the rigidity of the first substrate. The piezoelectric film sensor according to claim 4 .

6. The second substrate is divided into a plurality of members. The piezoelectric film sensor according to claim 5 .

7. The second base material divided into a plurality of members is arranged at a distance from one another. The piezoelectric film sensor according to claim 6 .

8. The second substrate is thinner than the first substrate. The piezoelectric film sensor according to claim 5 .

9. The second substrate has a notch. The piezoelectric film sensor according to claim 5 .

10. The notch is disposed below the second base material in a direction opposite to the first direction. The piezoelectric film sensor according to claim 9 .

11. a piezoelectric film having a first major surface and a second major surface; a first electrode disposed on the first major surface; a second electrode disposed on the second main surface; a first substrate disposed between the second electrode and an adherend; are laminated to form a laminate structure, The laminate structure is placed on a curved surface and pulled from both ends to bend the laminate structure convexly in a first direction from the first substrate toward the first electrode. Manufacturing method of piezoelectric film sensor.

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